Trash tolerant filter support for a disc filter

ABSTRACT

A filter device for filtering a liquid which includes trash. The device includes a drum for receiving the liquid and trash, wherein the drum includes at least one drum aperture. The device further includes a first pair of filter panels which are adapted for filtering the liquid. The filter panels are spaced apart to form a cavity for receiving the liquid and trash. The device further includes a frame for supporting the filter panels, wherein the frame is coupled to the drum. The frame includes a frame aperture wherein the frame aperture and the cavity form a volume having a cross sectional area sized substantially equal to or greater than the drum aperture and wherein said volume extends to a second pair of filter panels to enable liquid and trash which pass through the drum aperture to also pass through the frame aperture to the second pair of filter panels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/173,517 filed on Jul. 15, 2008 which in turns claims the benefit ofpriority to U.S. Provisional Patent Application Ser. Nos. 60/950,476 and60/950,484 both filed on Jul. 18, 2007.

FIELD OF THE INVENTION

The invention relates to a disc filter used in a wastewater treatmentplant, and more particularly, to a disc filter having a filter supportconfiguration which enables unimpeded flow of air and water betweenpairs of filter panels of the disc filter.

BACKGROUND OF THE INVENTION

Large water filtration systems frequently include one or more stages offiltration that clean the influent (typically water) to a sufficientlevel to allow for the discharge of the influent into a natural body ofwater such as a lake or river. In regions where water is scarce, it maybe desirable to further filter the water to allow for “reuse” of thewater.

Many wastewater treatment plants utilize a disc filter system to filterwater. Such systems typically include a plurality of discs eachincluding a plurality of filter segments. Each filter segment includes apair of filter panels which are spaced apart and arranged on an outersurface of the drum. A cap is attached to the top of each pair of filterpanels to thus form a pocket shaped filter segment for receiving water.Each filter panel includes filter media, such as finely woven cloth forfiltering water.

Each filter panel is attached to the drum by a filter supportarrangement. Each filter support includes a plurality of supportopenings which provide fluid communication between adjacent filtersegments. This enables water and air to flow circumferentially betweenadjacent filter segments as the drum rotates, thus resulting in anincrease in capacity of the disc filter system.

In operation, the drum is rotated and the water to be filtered isintroduced into the drum. The water then exits through ducts in the drumand flows into filter segments inside the filter support The water inthe filter support is then filtered through the media of the filterpanels to provide filtered water. The filtered water is then collectedin a chamber and exits the disc filter through an effluent pipe.Particulates which are filtered out by the filter panels remain withinthe filter segments on the inside surface of the filter media of thefilter panels. A spray device is used to spray the panels with water todislodge the particulates and clean the filter media. The particulatesare then collected onto a trough and are removed from the disc filtersystem.

The drum ducts used in conventional systems are of sufficient size toallow large rags, weeds, algae, fibrous assemblages and other trash topass through unimpeded. By way of example, the ducts may beapproximately 4-8 square inches in area. By contrast, the total area ofthe support openings between filter segments is substantially smallerand may be in the range of approximately 1 square inch. Duringoperation, trash is able to pass through the drum ducts but may notreadily pass through the smaller support openings. As a result, trashaccumulates at the support openings between filter segments which thencauses the support openings to become either partially or completelyblocked, thus impeding or stopping the flow of water between adjacentfilter segments. This results in turbulent flow inside the filtersegments, reducing the flow of particulates into the capture trough,thus increasing operating costs. Further, the support openings cannot beeffectively reached and thus cleaned by current spray devices,necessitating frequent stoppages of the disc filter system to allow formanual cleaning of the system in order to maintain operatingeffectiveness. Therefore, it is desirable to provide a disc filtersystem in which the amount of trash collected at the support openings issubstantially reduced.

SUMMARY OF THE INVENTION

The invention is directed to a filter device for filtering a liquidwhich includes trash. The device includes a drum for receiving theliquid and trash, wherein the drum includes at least one drum aperture.The device further includes a first pair of filter panels which arespaced apart to form a cavity for receiving the liquid and trash,wherein the filter panels are adapted for filtering the liquid.

The device further includes a frame for supporting the filter panels,wherein the frame is coupled to the drum and includes a frame aperture,wherein the frame aperture and cavity form a volume having a crosssectional area sized substantially equal to or greater than the drumaperture and wherein said volume extends to a second pair of filterpanels to enable liquid and trash which pass through the drum apertureto also pass through the frame aperture to the second pair of filterpanels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially broken away side view of a disc filter including aplurality of filter panels embodying the invention;

FIG. 2 is a broken away side view of the disc filter of FIG. 1;

FIG. 3 is a side view of a drum of the disc filter of FIG. 1;

FIG. 4 is a broken away view of a portion of a disc of the disc filterof FIG. 1;

FIG. 5 is a front schematic view of a portion of the disc filter of FIG.1;

FIG. 6 is a side schematic view of a portion of the disc filter of FIG.1;

FIG. 7 is a schematic front view of a disc of the disc filter of FIG. 1;

FIG. 8 is a perspective view of a disc of the disc filter of FIG. 1;

FIG. 9 is a front view of a filter panel in a support frame attached tothe drum of the disc filter of FIG. 1;

FIG. 10 is a perspective view of the filter panel of FIG. 9;

FIG. 11 is a front view of the filter panel of FIG. 9;

FIG. 12 is a schematic illustration of a feathered frame and a featheredstringer supporting a pleated filter media;

FIG. 13 is a schematic view of a backwash nozzle arrangement disposedbetween two adjacent discs of the disc filter of FIG. 1;

FIG. 14 is a side schematic view of the backwash spray bar arrangementof FIG. 13;

FIG. 15 is a perspective view of a mold configured to form a filterpanel;

FIG. 16 is an end view of the drum of FIG. 3;

FIG. 17 is another end view of the drum of FIG. 3;

FIG. 18 is a perspective view of the drum of FIG. 3;

FIG. 19 is a section view of a portion of the filter panel of FIG. 11taken along line 19-19 of FIG. 11;

FIG. 20 is a section view of a portion of the filter panel of FIG. 11taken along line 20-20 of FIG. 11;

FIG. 21 is a section view of a portion of the filter panel of FIG. 11taken along line 21-21 of FIG. 11;

FIG. 22 is a section view of a portion of the filter panel of FIG. 11taken along line 22-22 of FIG. 11;

FIG. 23 is a graph illustrating the reduced turbidity of fluid thatpasses through a filter as illustrated herein;

FIG. 24 is a perspective view of components that form a filter supportframework;

FIG. 25 is a side view of a filter support framework during theinstallation of a gasketed filter element;

FIG. 26 is an enlarged side view of a portion of the filter supportreceiving the gasketed filter element;

FIG. 27 is a perspective view of a snap lock feature;

FIG. 28 is a perspective view of a filter support;

FIG. 29A is a perspective view of the filter support shown in FIG. 28attached to a drum.

FIG. 29B is an end view of the filter support of FIG. 28 attached to adrum;

FIG. 30 is side view of a disc including several filter panels andfilter supports;

FIG. 31 is an end view of another filter support attached to a drum;

FIG. 32 is an end view of several filter supports attached to oneanother;

FIG. 33 is a perspective view of a disc including a number of filterpanels;

FIG. 34 is a perspective schematic illustration of an alternatearrangement wherein the filter panels of a disc are offset with respectto one another; and

FIG. 35 is a front schematic illustration of the alternate arrangementof FIG. 34.

DETAILED DESCRIPTION OF THE INVENTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. For example, the teachings of thisinvention apply not only to disc filters, but also may be adapted todrum type and other type filters that are used to filter high volume,high solids content fluids. The teachings apply not only to “inside-out”type filters using liquid head difference as a filtration driving force,but also apply to vacuum type filters, including “outside-in” typefilters, and filters that operate in an enclosed vessel under pressure.Such type filters are exemplified and described in more detail in thebrochures titled REX MICROSCREENS published by Envirex and dated August1989, REX Rotary Drum Vacuum Filters published by Envirex, and REXMICROSCREENS Solids Removal For Lagoon Upgrading, Effluent Polishing,Combined Sewer Overflows, Water Treatment, Industrial WastewaterTreatment and Product Recovery published by Envirex in 1989 which arehereby incorporated herein by reference in their entirely. Also, it isto be understood that the phraseology and terminology used herein is forthe purpose of description and should not be regarded as limiting. Theuse of “including,” “comprising,” or “having” and variations thereofherein is meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Unless specified or limitedotherwise, the terms “mounted,” “connected,” “supported,” and “coupled”and variations thereof are used broadly and encompass direct andindirect mountings, connections, supports, and couplings. Further,“connected” and “coupled” are not restricted to physical or mechanicalconnections or couplings.

While the invention illustrated herein is described as being employed ina waste water treatment setting, and particularly as a tertiarytreatment system, other uses and arrangements are possible. Otherwastewater treatment applications include use as a primary or secondaryclarifier in a municipal wastewater treatment plant as well asdetrashing sludge.

In addition to wastewater treatment uses, the present invention can beused in pulp and paper applications. For example, the invention can beused for white water filtration, improving water quality after save-allfilters, fiber recovery, raw water screening in the production ofmechanically purified process water, prefiltration in conjunction with asand filter in the production of chemically purified water, treatment ofsealing water for pumps, recirculating the water in wood rooms,thickening pulp and paper stock, and/or replacing Vacuum filters, suchas those commonly used in the pulp and paper industry (outside-in flow).

Still other applications include but are not limited to, dewateringcoal, taconite processing, service water treatment, cooling watertreatment, treating wastewater from galvanization processes, separationof tobacco particles from wastewater, and/or food industry wastewaterfiltration.

FIG. 1 illustrates a possible disc filter system configuration 10employing pleated filter media 15. The media 15 may be woven ornon-woven. In addition, pile cloth, needle felt, microfiltration,nanofiltration, reverse osmosis, or other membranes may be employed asmedia constructions. Preferred materials for use in making filter mediainclude but are not limited to polyester, metal-coated polyester,antimicrobial-coated polyester, polypropylene, nylon, stainless steelwire, glass fiber, alumina fiber, glass filled polypropylene (17%preferred), glass-filled acetal, and/or glass-filled nylon.

It should be noted that the term “filter media” should be interpretedbroadly to cover any component that filters a fluid. Other termsincluded within the definition of filter media include membrane,element, filter device, and the like. As such, the term “filter media”should not be narrowly interpreted to exclude any component that filtersfluid.

Referring to FIGS. 1 and 2, disc filter 10 includes a housing 20, suchas a metal tank that substantially encloses a drum 25, a plurality ofdiscs 30, a drive system 35, and a flow system 40. It will beappreciated that variations on this design, including those employing aframe intended to facilitate mounting of the unit in a concrete tank,are also commonly used. The drive system 35 includes at least twobearings that support the drum 25 for rotation. A driven sprocket 50 iscoupled to the drum 25 and a drive sprocket 45 is coupled to a motor 55or other prime mover. In the illustrated construction, a belt engagesthe drive sprocket 45 and the driven sprocket 50 such that rotation ofthe motor 55 produces a corresponding rotation of the drum 25. Inpreferred constructions, the sprockets 45, 50 are sized to produce asignificant speed reduction. However, some constructions may employ aslow speed drive with no speed reduction if desired. While theillustrated construction employs a belt drive, other constructions mayemploy gears, shafts, chains, direct drive, or other means fortransferring the rotation of the motor 55 to the drum 25.

The flow system 40, better illustrated in FIG. 2, includes an influentpipe 60 that directs influent into an interior 65 (see FIG. 9) of thedrum 25, an effluent pipe 70 that directs filtered fluid from a chamber75 defined within the housing 20 out of the filter 10. A spray waterpipe 80 provides high-pressure water to a spray system 85 (shown inFIGS. 5 and 13) that is periodically used to clean the filter media 15.A backwash pipe 90 transports the spray water after use and directs itout of the disc filter 10.

The disc filter 10 of FIGS. 1 and 2 employs a plurality of discs 30 toincrease the overall filter area. The number and size of the discs 30can be varied depending on the flow requirements of the system. Forexample, additional discs 30 can be attached to the drum 25 to increasethe capacity of the filter system 10 without having to pass additionalflow through any of the already existing discs 30.

FIGS. 3 and 16-18 illustrate a possible drum configuration 25 that issuitable for use with the invention. The illustrated drum 25 includes anouter surface 95 and two end surfaces 100 that cooperate to define theinterior space 65. One end is open to permit flow and the other end issealed against flow. Several drum apertures 105 are arranged in a seriesof axial rows with each row including a number of drum apertures 105that extend circumferentially around a portion of the outer surface 95.The drum apertures 105 are rectangular although it is understood thatother shapes may be suitable. Attachment apertures 110 are positioned oneither side of each drum aperture 105. Each drum aperture 105 isassociated with a set of attachment apertures 110.

As illustrated in FIGS. 3 and 16-18, the outer surface 95 of the drum 25includes a number of flat planar surfaces 115 that contact one anotherto define a polygonal cross section. A circular cross section or acylindrical or other shape could be employed in the invention ifdesired.

Referring to FIG. 5, a side view of one of the discs 30 of FIGS. 1 and 2is shown. Each disc 30 includes a plurality of filter panel sets 300.Each filter panel set 300 includes two associated filter panels 125. InFIG. 5, one of the filter panels 125 from each panel set 300 is shown.The disc 30 in FIG. 5 depicts twelve filter panels 125 and thus disc 30includes a total of twenty four filter panels 125. However, otherconstructions may employ more or fewer filter panels 125 as desired. Forexample, FIGS. 7 and 8 illustrate another arrangement in which twentyeight filter panels 125 are used (i.e. 14 filter panel sets).

Referring to FIG. 4, one of the filter panel sets 300 is depicted. FIG.4 is a side view of FIG. 9 with a right portion of a support structure150 (see FIG. 9) removed. The filter panels 125 are mounted in thesupport structure 150 such that the filter panels are spaced apart fromeach other. An attachment plate 155 having an aperture 145 engages theattachment apertures 110 around a drum aperture 105 to attach thesupport structure 150 to the drum 25. A cap 175 is located over a topportion of the filter panels 125. The filter panels 125, the supportstructure 150 in which they are mounted, the cap 175, and the attachmentplate 155 define a partially enclosed space 180. The partially enclosedspace 180 extends circumferentially around the drum 25 through eachfilter panel set 300 on the disc 30. Fluid is able to pass from withinthe drum 25, through the drum aperture 105 and aperture 145 in theattachment plate 155 and into the enclosed space 180 to enable fluid toflow circumferentially within each filter panel set in the disc 30, aswill be discussed below. A perimeter seal 165 is located on a perimeter170 of each filter panel 125 (see FIGS. 10 and 11) and serve to inhibitleakage of water from around the filter panel 125.

Referring to FIG. 2 in conjunction with FIGS. 5 and 6, the spray waterpipe 80 extends the full length of the disc filter 10 and defines adistribution manifold 185. A spray bar 190 is positioned betweenadjacent discs 30 (see FIG. 14) and at each end of the disc filter 10. Adistribution pipe 195 extends between the manifold 185 and the spray bar190 to provide for fluid communication of high-pressure water to thespray bar 190. The spray bar 190 includes nozzles 200 that spray wateronto the filter panels 125 to periodically clean the filter panels 125as will be described in greater detail with reference to FIGS. 13 and14.

A trough 205 is positioned beneath the spray bar 190 between adjacentdiscs 30 to catch the spray water or backwash, including any particulatematter removed from the filter panels 125. The backwash and particlesare then removed from the system 10 via the backwash pipe 90.

FIGS. 9 and 10 illustrate possible arrangements of the filter panels125. FIG. 9 illustrates the panel 125 mounted in the support structure150 (see also FIG. 4). FIG. 10 illustrates a pleated panel. The filterpanels 125 include a pleated filter media 15, a perimeter frame 210, andseveral support gussets or stringers 215. In most constructions, thestringers 215 are molded as an integral part of the frame 210 with otherattachment means also being suitable for use. In preferredconstructions, the pleated filter media 15 is formed from a single pieceof material that is sized and shaped to fit within the perimeter frame210. In the illustrated constructions, the pleats extend in asubstantially radial direction with other orientations also beingpossible. In one construction, a stainless steel screen is employed asthe filter media 15. Other constructions may employ woven polyester,cloth, or other materials. The materials used and the size of theopenings are chosen based on the likely contaminates in the effluent,the flow rate of the effluent, as well as other factors. In preferredconstructions, the openings are between about 10 and 20 microns withsmaller and larger openings also being possible.

The cap 175 is preferably formed from extruded aluminum with othermaterials (e.g., plastic, stainless steel, etc.) and other constructionmethods (e.g., injection molding, forging, casting, etc.) also beingpossible. In the illustrated construction, straight extruded portionsare welded together to define the cap 175.

FIGS. 11 and 19-22 illustrates another arrangement of a filter panel 125that includes a one-piece pleated filter media disposed within a frame210. The construction of FIGS. 11 and 19-22 is similar to theconstruction of FIGS. 9 and 10 but also includes reinforced crossbracing 220 and peak stiffening members or ridge bars 225. In general,the ridge bars 225 and the stringers 215 cooperate to subdivide thefilter media into a plurality of smaller cells. The cells are preferablysized as will be discussed below.

Before proceeding, it should be noted that stringers 215, cross braces220, and ridge bars 225 are reinforcing members that aid in maintainingthe pleated shape of the pleated filter media. It is understood thatother reinforcing members or arrangements of the reinforcing membersdescribed herein which are suitable for maintaining the pleated shape ofthe filter media may also be used.

As illustrated in FIG. 19, one construction of the frame 210 is formedwith a cross section of an angled member that includes a flow-parallelleg 230 and a flow-transverse leg 235 (see also FIG. 10). Theflow-transverse leg 235 receives the respective inner diameter seal 165as illustrated in FIG. 4, and provides additional stiffness to theflow-parallel legs 230. The flow-parallel legs 230 are sized tosubstantially match the peak-to-peak height of the pleated filter media15. Referring back to FIG. 10, the frame 210 also includes twosubstantially parallel sides 236 and two non-parallel sides 237 that arearranged such that they are substantially radial with respect to thedrum 25.

To further stiffen the filter media 15, a series of stringers 215 extendacross the opening in the frame. The stringers 215 include saw toothcuts 238, illustrated in FIG. 21 that fit within the pleats to aid inholding the pleated filter media 15 in the desired shape. Theconstruction of FIGS. 9, 10 and 11 includes four stringers 215 althoughit is understood that three stringers 215 or other constructions may beused. In most constructions, the stringers 215 are molded as an integralpart of frame 210 although other suitable attachment methods may also beused. As illustrated in FIG. 21, the stringers 215 are generally locatedon both sides of the pleated filter media 15 such that the media 15 issandwiched between two opposite stringers 215. This arrangement aids inholding the pleated filter media 15 in place during normal filteringoperation as well as during backwashing.

As previously described, the construction of FIG. 11 includes additionalpeak stiffening members or ridge bars 225 that are coupled to the peaksand/or the valleys of the pleats. As illustrated in FIG. 20, plastic canbe molded to the peaks and valleys to define the ridge bars 225 andfurther stiffen the media 15. Alternatively, metal wires or rods ofmetal, fiberglass-reinforced plastic, or other material of sufficientstiffness can be positioned to maintain the shape of the peaks and thevalleys.

In still other constructions, reinforced cross bracing 220, such as thatillustrated in FIG. 22 can be employed to further stiffen the pleatedfilter media 15. Again, molded plastic may be employed as cross bracing220. Additionally, metal wire or bars may be welded, brazed, orotherwise attached to the pleated filter media 15 as cross bracing 220.

In still other constructions, two pleated filter media 15 pieces arepositioned in a back to back relationship such that they provide supportfor one another.

Referring to FIG. 15, another construction is shown. In thisconstruction, the filter panels 125 are molded using a plastic materialin conjunction with a filter media 15 or filter member. In thisconstruction, a substantially planar sheet of the filter media 15 isplaced in a mold 335. The mold 335 includes a first half 340 and asecond half 310 that close over the filter media 15 and create thepleats in the media 15. A plastic material is then injected into themold 335 to form the perimeter frame 210, the stringers 215, and theridge bars 225. Thus, the perimeter frame 210, the stringers 215, andthe ridge bars 225 are integrally formed as a single piece or componentaround the filter media 15. The edges of the filter media 15 areembedded in the perimeter frame 210, the ridge bars 225 are adjacent toor molded around the peaks and valleys of the pleats, and the stringers215 are formed with saw tooths that engage the pleats. The pleats of thefilter media 15 are sandwiched between the saw tooths of the stringers215.

Referring to FIG. 12, feathering 240 may also be employed at some or allof the interfaces to reduce fatigue and improve the overall life of thepleated filter media 15. FIG. 12 illustrates a feathered frame 210 a anda feathered stringer 215 a adjacent the frame 21 Oa. The feathering 240provides additional surface area contact between the feathered component(e.g., frame, stringer, etc.) and the pleated filter media 15.Feathering 240 reduces the overall fatigue damage that may occur, andthus may extend the operational life of the pleated filter media 15.

FIG. 13 illustrates a possible arrangement of nozzles 200 on a spray bar190. As previously described, spray bars 190 are positioned betweenadjacent discs 30 and at the ends of the disc filter 10 to enable thespraying of high-pressure water in a reverse flow direction through thepleated filter media 15 to provide backwashing of the filter media 15.Because the filter media 15 is pleated and thus angled with respect tothe plane of the discs 30, the use of nozzles 200 that are similarlyangled provides for more efficient backwash cycles. Thus, the nozzles200 are angled approximately 45 degrees off of a normal direction to theplanes of the discs 30. In addition, two nozzles 200 are provided ateach spray point 244 (see FIG. 14) with the nozzles 200 angled withrespect to one another at about 90 degrees such that both sides of thepleats are sprayed directly during the backwashing. Surprisingly, astraight on direct spray may be utilized. In addition, bouncing sprayoff the filter media at an angle improves the cleaning effect andefficiency for a given amount of backwash flow and spray velocity.

As illustrated in FIG. 14, each spray bar 190 may include multiple spraypoints 244 with four nozzles 200 supported at each spray point 244. Inthe construction illustrated in FIG. 14, six spray points 244 areemployed with more or fewer points being possible. As the discs 30rotate, the nozzles 200 direct high-pressure water onto the pleatedfilter media 15 and clean the filter media 15. It should be noted thatthe endmost spray bars 190 only require two nozzles 200 per spray point244 as they are not disposed between two adjacent discs 30.

Referring to FIG. 28, a filter support 245 in accordance with thepresent invention is shown. The filter support serves to support aportion of a side 255 and bottom portion 250 of a pair of filter panels125 (see FIG. 11). The filter support 245 includes an attachment portion260 and a transversely oriented strut portion 270. The attachmentportion 260 includes a first section 265 which extends from an end 267of the strut portion 270. The attachment portion 260 also includes asecond section 269 which extends from the end 267 in a directionopposite to the first section 265 to thus form an inverted T-shapedfilter support 245. The attachment portion 260 further includes a singleaperture 275 which extends along the first 265 and second 269 sectionsof the attachment portion 260 and along the strut portion 270 to thusform a substantially inverted T-shaped aperture which corresponds to theshape of the filter support 245.

Referring to FIG. 29A, the filter support 245 is shown positioned on thedrum 25. The attachment portion 260 is designed to be maintained inalignment with drum aperture 105 such that the aperture 275 is in fluidcommunication with an associated drum aperture 105 in the drum 25. Theaperture 275 is substantially the same size or larger than the drumaperture 105. In another embodiment, the filter support 245 ispositioned on the drum 25 such that the attachment portion 260 straddlesa support section of the drum 25 located in between adjacent drumapertures 105. In this embodiment, portions of two adjacent drumapertures 105 are in fluid communication with the aperture 275.

Referring to FIG. 29B, a pair of filter panels 125 is shown installed inthe filter support 245. The filter panels 125 are spaced apart from eachother. Referring to FIG. 30 in conjunction with FIG. 33, a side view ofa plurality of filter supports 245 and filter panels 125 is shown. A cap295 is used to secure each pair of filter panels 125. Each cap 295 isremovably secured to adjacent radial struts 270 to enable removal ofeach filter panel 125 for cleaning or replacement as necessary. Eachfilter panel pair, filter support 245 and associated cap 295 form afilter panel set 300 for receiving contaminated water. Further, thefilter panels 125, cap 295 and aperture 275 form a volume 182 whosecross sectional area is equal to or larger than the area of drumaperture 105. Volume 182 extends circumferentially around the drum 25through each filter panel set 300 on the disc 30 and is continuous.Referring to FIGS. 30, 29A, 29B, and 30 in conjunction with FIG. 33, theaperture 275 enables fluid communication between the drum aperture 105and adjacent filter panel sets 300. This enables water and air to flowcircumferentially between adjacent filter panel sets 300 as the drum 25rotates, thus resulting in an increase in capacity of the disc filter10.

Water to be filtered enters a filter panel set 300 through the drumaperture 105 and the aperture 275. The water in the filter panel set 300is then filtered through the filter panels 125 to provide filteredwater. The aperture 275 is of sufficient size relative to the drumaperture 105 such that trash or other debris which flows through thedrum aperture 105 is not captured by the radial strut 270. In oneembodiment, the aperture 275 is substantially equal in size to the drumaperture 105. In another embodiment, the aperture 275 is sized largerthan the drum aperture 105. As a result, the amount of trash collectedby the radial strut 270 is substantially reduced or eliminated,resulting in relatively unimpeded flow of water and air between filterpanel sets 300 as the drum 25 rotates. This design feature minimizeswater turbulence from water inertia and prevents air entrapment andsubsequent release so that the undesirable wash off of solids alreadyfiltered from the water is substantially reduced. The radial strut 270further includes ribs 305 which provide structural support.

Referring to FIG. 31, a filter support 317 is shown wherein the radialstrut 270 includes a gusset 312 which provides additional structuralsupport. The filter support 317 includes first 315 and second 320 fluidchannels whose total area is substantially equal in size to the drumaperture 105. This results in the elimination or reduction in the amountof trash that is collected by the radial strut 270 as described above.Filter support 317 results in a larger fluid channel area relative tothat of conventional filter supports. This reduces the amount ofmaterial necessary to manufacture filter supports 317, thereby resultingin reduced manufacturing costs. It has been determined throughcalculation that the structural integrity of the embodiments shownherein are acceptable when designing for a head loss of as much as 24inches of water or even higher.

As previously described, the disc filter 10 may use filter panels 125which are pleated, although it is understood that other types of panelsmay be used. An advantage with using pleated filter media 15 is thatboth the media pleats themselves, as well as the panel perimetersidewalls such as those along the radial sides of the pleated panel 125,provide temporarily horizontal surfaces to which trash can cling morereadily. As a result, rotating shelves are formed while submerged whichare oriented at a favorable angle with respect to gravity until thetrash is over the trough for eventual deposit thereon.

Referring to FIG. 32, a plurality of filter supports 245 is shownassembled. The radial struts 270 extend outwardly from the drum 25 andare spaced apart from each other to form spaces 325 each of which isadapted to receive a filter panel 125. Referring to FIG. 33, a view ofthe disc 30 is shown depicting filter supports 245, filter panels 125and caps 295 in accordance with the present invention. In thisconfiguration, the disc includes fourteen filter panels sets 300 (twentyeight filter panels 125 total).

In prior designs, seating of the panels is a two-step process. First,the filter panel with edge seal is slid down into the edge channels of afilter support. Then the cap is slid into place against the top edgegasket. During the both steps, sliding friction develops between thechannel walls and the gasket. During the first step, the maximum panelseating force required can rise to a very large value unless a designcompromise is made. Along the angled sides 255 of the trapezoidal panel,the friction force direction is opposite to the gasket insertion path,but is at a significantly oblique angle to the long direction of thegasket. Hence, the risk of sideways stretching or potentially distortingmovement of the gasket relative to its original position and shape ishigh. Such distortion may result in leakage. In particular, the gasketcan seal against higher pressure if under a higher compression force,but high compression force raises the risk of leakage due to distortionor stretching of the gasket during insertion into the angled sidechannels of a conventional design.

The friction associated with gasket sliding in a filter supportstructure design having sidewall channels demands a compromise betweenreasonable insertion force and adequate compression of the gasket. Lowergasket compression results in lower sliding friction, but also reducesthe pressure threshold for leakage. Conventional systems attempt toovercome this problem by “flocking” the outside sliding surfaces of therubber gasket. While this helps, it does not eliminate the inherentproblem.

In a preferred embodiment, a bottom channel is used. Since the bottomchannel is relatively short the insertion force remains very low, evenfor reasonably high gasket compression. The likelihood of sidewaysstretching or potentially-distorting movement of the gasket due tooblique friction forces is substantially reduced for a bottom channel.

To assemble a filter panel 125, a molded gasket 500 that is slightlyundersized is stretched around the outside of the filter panel 125 tocreate a gasketed panel 505 as illustrated in FIGS. 25 and 26. Thetension on the gasket 500 serves to hold the gasket 500 in position.However, some constructions may employ a sealing/retention aid such assilicone rubber or silicone grease. The bottom of the gasketed panel 505is then inserted into a filter panel receiving space such as a slot orbottom channel 510 of the filter support 245 (shown in FIG. 24) and ispushed downward. The top of the gasketed panel 505 is then pushedforward (tilted) to lock the panel 125 in place.

In one embodiment, the filter support 245 includes a snap lock feature520 (shown in FIG. 27) located about one quarter of the way from the topof the filter support 245. More specifically, the snap lock feature 520is on the radial strut 270 of the filter support 245. Each snap lockfeature 520 holds two adjacent filter panels 505. The snap lock feature520 is flexible, and is pushed out of the way as the panel 505 is tiltedinto place. It then snaps back to its original position, locking thepanel 505 into the upright position. In this position (the operatingposition) a seal is formed completely around the perimeter of the filterpanel 505 between the filter panel 505 and the panel support structure,which includes the filter support 245 and the cap 295.

To complete the installation of the gasketed panels 505, the cap 295 ispositioned on top of the filter support structure and cap hardware isinstalled. In preferred constructions, the cap hardware includes a nutand a bolt that connect the cap 295 to the adjacent cap 295. Each end ofthe cap 295 is connected to the adjacent cap 295 to define a completering of caps 295 around the outer perimeter of the disc 30.

In operation, water enters the disc filter 10 via the influent pipe 60.The contaminated influent water is separated from the clean filteredwater using a wall 76 through which the drum is mounted with a rotatingseal. The wall 76 forms an influent water chamber 77 and a filtratewater chamber 75. The influent enters the drum interior 65 and exitsthrough drum apertures 105 in the drum 25 and flows into volume 182 aspreviously described. The water in volume 182 is then filtered throughthe pleated filter media 15 in at least one of the filter panels 125 andflows out (“inside out flow”) to provide filtered water. As the influentpasses through the pleated filter media 15, particulates that are largerthan the openings in the filter media 15 are retained within volume 182and remain on an inside surface of the filter media 15. The effluentcollects within the filtrate water chamber 75 outside of the discs 30and exits the disc filter 10 via the effluent pipe 70. A system of weirsdefines the effluent end of filtrate water chamber 75 and maintains thedesired minimum liquid level in chamber 75 within the filter 10.

During operation, the drum 25 continuously or intermittently rotatessuch that filter panels 125 enter the liquid and filter influent onlyduring a portion of the rotation. As previously described in relation toFIGS. 28, 29A, 29B and 30, the aperture 275 enables fluid communicationbetween the drum aperture 105 and adjacent filter panel sets 300. Thisenables water and air to flow circumferentially between adjacent filterpanel sets 300 as the drum 25 rotates. As a result, the amount of trashcollected by the radial strut 270 is substantially reduced oreliminated, resulting in relatively unimpeded flow of water and airbetween filter panel sets 300 as the drum 25 rotates. This designfeature minimizes water turbulence from water inertia and prevents airentrapment and subsequent release so that the undesirable wash off ofsolids already filtered from the water is substantially reduced.

Since discs 30 are never fully submerged, filter panels 125 enter theliquid and are available for filtering influent only during the bottomportion of the rotation arc. After filtering, and during rotation ofdrum 25, the filter panels 125 exit the liquid and pass the spray bars190. During a backwash cycle, the spray device 85 is used to spray thefilter panels 125 with high-pressure water or chemicals to dislodge theparticulates and clean the filter media 15 as the drum 25 rotates. Thewater droplet impact vibration and penetration of the filter media 15 bya portion of the water removes debris that is caught on the upstreamsurface of the pleated filter media 15. The debris and water arecollected in the trough 205 and transported out of the filter system 10by pipe 90. During backwashing, filtration can continue as some of thefilter panels 125 are disposed within the liquid, while others are abovethe liquid and can be backwashed.

The filter panels 125 described herein provide for a greater flow areathan prior art systems and are capable of operating at a substantiallyhigher flow through a similar panel area. Specifically, the perimeterframe 210 defines a panel normal flow area 350, shown in FIG. 9 that isessentially the planar area within the perimeter frame 210. As one ofordinary skill will realize, the true flow area is less than this planararea as support members may extend across this area and block some ofthe flow area. However, this area is minimal and generally can beignored. By forming pleats in the filter media, the flow area is greatlyincreased as the fluid (e.g., air, water) flows generally through thepleats in a direction 355 normal to the pleat, as illustrated in FIG.10. Thus, the pleats define a media normal flow area 360 that issubstantially greater than the panel normal flow area 350. Essentially,the media normal flow area 360 is the sum of the areas of the variouspleats measured in a plane normal to the flow direction 365. In oneconstruction, the media normal flow area 360 for each filter panel 125is greater than one square foot (0.09 sq meters) with sizes greater thantwo square feet (0.19 sq meters) being preferred. Test data shows thatthis flow area provides for a flow rate through each filter panel inexcess of about 7 gallons per minute (26.5 liters per minute). Morespecifically, each filter panel 125 is configured to pass a liquid flowtherethrough. The liquid flow is in excess of 3 gallons per minute persquare foot (11.4 liters per minute per 0.09 sq. feet) and is at apressure differential across the filter media in excess of 12 inches ofwater (3 kPa).

While the foregoing description should be read to include manyvariations of pleats, the following table illustrates the expected lowend, the expected high end, and the expected nominal size of severalparameters of the pleats. Of course variations in these parameters maybe possible.

Parameter Low End Nominal High End Cell Size, inches 0.5 × 0.5 0.75 × 42 × 36 (mm) (12.7 × 12.7) (19 × 102) (51 × 914) Pleat Height, inches  0.1 1.0 6.0 (152)   (mm)   (2.5) (25.4) Pleat Included Angle, 20  6080 Degrees Velocity past Cleaning 1  3 to 30 50 (15.25) Nozzles ft/min  (0.3) (0.9 to 9.1) (meters/min) Head Loss, inches of water 0 12-2436-48 (meters of water) (0)  (0.3-0.61) (0.91-1.22) Flux Media Normal,gpm/ 0 3-6 15 (611.2) sq ft (liters per minute/sq meter) (0)(122.2-244.5) Solids Loading, lbs/day/ 0 2 20 (95.8)  sq ft (kg/day/sqmeter) (0) (9.58)

It should be noted that the low end pleat height is based on amicropleat design with thin panels having many tiny pleats, while thehigh end design is based on a thick panel design. In addition, the lowend included angle is possible due to the unexpected finding that solidscan be easily removed from the valleys, and that the risk of beingunable to clean the valleys was very low. The velocity past the cleaningnozzles is at least partially a function of the size of the discs withsmaller discs allowing for higher angular velocities.

While there are many variations of the design described herein, onefilter has been field tested and produced a reduction in turbiditymeasured in Nephelometric Turbidity Units (NTU) as illustrated in thegraph of FIG. 23. Of course other arrangements may provide better orworse performance depending on the particular arrangement.

It should be noted that the invention described herein is alsowell-suited for existing applications. For example, an existing filtercan be modified to incorporate the present invention. Such amodification would increase the flow rate and reduce the pressure dropthrough the filter without increasing the footprint of the filter. Inthis application, the existing non-pleated filter media is removed fromthe drum. Filter supports are coupled to the drum and pleated filterpanels are inserted into the filter supports to complete themodification. In preferred constructions, the filter supports are moldedfrom plastic with other materials (e.g., metal) also being suitable foruse.

While most of the figures illustrate discs 30 that include filter panels125 that are substantially aligned, FIGS. 34 and 35 illustrate anotherarrangement in which the filter panels 125 on a first side 1285 of thedisc 30 are rotated with respect to the filter panels 125 on a secondside 1290 (shown in broken lines) of the disc 30. In the arrangement ofFIG. 34, the center axis 1287 for each panel 125 on the first side 1285of disc 30 is offset relative to the center axis 1292 of each filterpanel 125 on the second side 1290 of the disc 30 to form offset filterpanel pairs. By way of example, the filter panel pairs may be offset bya first distance 1297 equal to approximately half of a filter pair 1300.

Thus, the invention provides, among other things, a new and usefulfilter panel 125 for use in a disc filter 10. The filter panel 125includes pleated filter media 15 that increases the overall surface areaper unit area that can be used for filtration, and retains the pleatedshape of the media against the turbulent and viscous forces generated athigh flow rates of liquid.

What is claimed is:
 1. A filter device for filtering a liquid whichincludes trash, the device comprising: a drum for receiving said liquidand trash wherein said drum includes at least one drum aperture; aplurality of filter devices for filtering said liquid, each said filterdevice having a cavity; and a frame for supporting said filter device,wherein said frame is coupled to said drum and includes a frame apertureand wherein said frame aperture and said cavity form a volume having across sectional area sized substantially equal to or greater than saiddrum aperture and wherein said volume extends through said filterdevices to enable liquid and trash which pass through said drum apertureto also pass through said frame aperture and through each of said filterdevices.
 2. The filter device according to claim 1, wherein said drumaperture is aligned with said frame aperture.
 3. The filter deviceaccording to claim 1, wherein said drum includes a support sectionlocated between adjacent drum apertures and said frame aperturestraddles said support section.
 4. The filter device according to claim1, wherein said frame aperture extends through an attachment portion anda strut portion of said frame.
 5. The filter device according to claim1, wherein said frame aperture forms an inverted substantially T-shapedconfiguration.
 6. The filter device according to claim 1, wherein saidfilter includes a filter media having a plurality of pleats.
 7. A filterdevice for filtering a liquid which includes trash, the devicecomprising: a drum for receiving said liquid and trash wherein said drumincludes at least one drum aperture; a first pair of filter panels whichare spaced apart to form a cavity for receiving said liquid and trash,wherein said filter panels are adapted for filtering said liquid; and aframe for supporting said filter panels, wherein said frame is coupledto said drum and includes a frame aperture and wherein said frameaperture and said cavity form a volume having a cross sectional areasized substantially equal to or greater than said drum aperture andwherein said volume extends to a second pair of filter panels to enableliquid and trash which pass through said drum aperture to also passthrough said frame aperture and through said first and second pairs offilter panels.
 8. The filter device according to claim 7, wherein saiddrum aperture is aligned with said frame aperture.
 9. The filter deviceaccording to claim 7, wherein said drum includes a support sectionlocated between adjacent drum apertures and said frame aperturestraddles said support section.
 10. The filter device according to claim7, wherein said frame aperture extends through an attachment portion anda strut portion of said frame.
 11. The filter device according to claim7, wherein said frame aperture forms an inverted substantially T-shapedconfiguration.
 12. The filter device according to claim 7, wherein saidfilter panels include filter media having a plurality of pleats.
 13. Thefilter device according to claim 7, wherein said drum includes at leastone disc having a plurality of filter panels for forming first andsecond panel sets wherein filter panels from said first panel set areoffset relative to filter panels of said second panel set.
 14. A filterdevice for filtering a liquid which includes trash, the devicecomprising: a drum for receiving said liquid and trash wherein said drumincludes at least one drum aperture; a plurality of filter panels forfiltering said liquid, said filter panels forming a plurality of discs;selectively rotating said drum to thus rotate said discs to enablefiltering of said liquid; frames for supporting said filter panels,wherein each frame is coupled to said drum and includes a frame apertureand wherein said frame aperture and said cavity for a volume having across sectional area sized substantially equal to or greater than saiddrum aperture and wherein said volume extends to a second pair of filterpanels to enable liquid and trash which pass through said drum apertureto also pass through said frame aperture and through said second pair offilter panels; and selectively backwashing said filter panels.
 15. Thefilter device according to claim 14, wherein said drum aperture isaligned with said frame aperture.
 16. The filter device according toclaim 14, wherein said drum includes a support section located betweenadjacent drum apertures and said frame aperture straddles said supportsection.
 17. The filter device according to claim 14, wherein said frameaperture extends through an attachment portion and a strut portion ofsaid frame.
 18. The filter device according to claim 14, wherein saidframe aperture forms an inverted substantially T-shaped configuration.19. The filter device according to claim 14, wherein said filter panelsinclude filter media having a plurality of pleats.
 20. The filter deviceaccording to claim 14, wherein said drum includes at least one dischaving a plurality of filter panels for forming first and second panelsets wherein filter panels from said first panel set are offset relativeto filter panels of said second panel set.
 21. A method for filtering aliquid which includes trash, the method comprising the steps of:receiving said liquid and trash in a drum; providing a first pair offilter panels for filtering said liquid; providing fluid communicationbetween said drum and a second pair of filter panels to enable liquidand trash from said drum to pass through said first pair of filterpanels to said second pair of filter panels.
 22. The filter deviceaccording to claim 21, wherein said filter panels are supported by aframe having a frame aperture and said drum includes a drum aperturewherein said drum and said frame aperture provides fluid communicationbetween said drum and said second pair of filter panels.
 23. The methodaccording to claim 22, wherein said drum includes a support sectionlocated between adjacent drum apertures and said frame aperturestraddles said support section.
 24. The filter device according to claim22, wherein said frame aperture extends through an attachment portionand a strut portion of said frame.
 25. The filter device according toclaim 22, wherein said frame aperture forms an inverted substantiallyT-shaped configuration.
 26. The filter device according to claim 22,wherein said filter panels include filter media having a plurality ofpleats.
 27. The filter device according to claim 22, wherein said drumincludes at least one disc having a plurality of filter panels forforming first and second panel sets wherein filter panels from saidfirst panel set are offset relative to filter panels of said secondpanel set.